RESUMO
Purpose@#Endocrine therapy is the first-line treatment recommended for patients with hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-negative metastatic breast cancer without visceral crisis. However, this recommendation has not been followed clinically because of efficacy issues. In this study, the survival of patients with HR-positive/HER2-negative metastatic breast cancer was evaluated based on the following first-line treatment regimens: the combination of palbociclib plus letrozole, conventional endocrine therapy, or chemotherapy. @*Methods@#Medical records were reviewed for this retrospective analysis. Patients with HR-positive/HER2-negative metastatic breast cancer were included. Progression-free survival (PFS) and overall survival (OS) were compared based on first-line treatment regimens. @*Results@#A total of 184 patients were included in the analysis. The first-line treatments were palbociclib plus letrozole in 46 patients (25.0%), endocrine therapy in 40 patients (21.7%), and chemotherapy in 98 patients (53.3%). The PFS of the palbociclib plus letrozole group was significantly longer than that of the endocrine therapy (hazard ratio=3.43, p<0.001) and chemotherapy (hazard ratio=2.88, p=0.001) groups. No significant difference was observed between the endocrine therapy and chemotherapy groups (p=0.430). The OS of the palbociclib plus letrozole group was significantly longer than that of the endocrine therapy (hazard ratio=5.34, p=0.009) and chemotherapy (hazard ratio 4.23, p=0.043) groups. No significant difference was observed between the endocrine therapy and chemotherapy groups (p=0.451). @*Conclusion@#The combination regimen of palbociclib and letrozole could be recommended as the first-line treatment of choice in patients with HR-positive/HER2-negative metastatic breast cancer.